Such well-known underwater installations include a riser pipe that extends from the seabed as far as an intermediate area overlying the seabed and situated below the surface and a flexible pipe connected to extend the riser pipe and that extends catenary fashion from the intermediate area to the surface. The riser pipe is kept substantially vertical by means of a float submerged in the intermediate area. This type of installation makes it possible to raise hydrocarbons from the seabed to the surface without being constrained by disturbances of the surface linked to swell, currents or winds.
The document WO2009/112 687 describes an underwater installation of this type. The underwater installation usually includes a frame or a turret enabling the end of the riser pipe and the float to be connected together, and the frame is equipped with a swan-neck pipe that extends the riser. The pipe has a free end provided with an end fitting. In a first installation phase, the frame and the float hold the riser pipe in vertical equilibrium. In a second installation phase the flexible pipe terminated by a connector is connected to the end fitting, from the surface, so as to establish the connection between the riser pipe and the flexible pipe. To this end, the connector is specifically equipped with a flange and is installed at the end of the flexible pipe. It approaches the frame as the flexible pipe is paid out from the surface. As for the frame, it includes retaining members and the flange is then engaged in the retaining members. More of the flexible pipe is paid out and the connector then tilts around the retaining means so that it faces the end fitting on the pipe. The connector is then driven toward the end fitting to connect them together.
Difficulties arise in connecting the connector to the end fitting at greater depths of water. In fact, the riser pipes are longer and consequently heavier. The same goes for the flexible pipes and the forces to be exerted on the connector are consequently higher. Now the latter connectors are fragile and costly. Moreover, during the phase of moving the connector and the frame closer to each other, and given the masses involved, the slightest impacts can have an impact on the integrity of the connector.